Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

974
FXUS63 KLOT 271953
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
253 PM CDT Fri Mar 27 2026

.KEY MESSAGES...

- Cooler temperatures again on Saturday before milder weather
  returns for Sunday and especially early next week.

- Elevated fire weather conditions Saturday and possibly again
  on Sunday.

- Stormy weather pattern returns early to middle of next week.

&&

.DISCUSSION...
Issued at 230 PM CDT Fri Mar 27 2026

Conditions are fairly quiet out there today on this relatively
cooler Friday. Temperatures this afternoon are sitting in the
upper 30s to lower 40s following yesterday`s `pneumonia` cold
front. The cold advection is allowing us to regularly mix 20 to
25 mph NW gusts down to the surface. Overcast skies lingering
behind the front finally cleared our CWA late this morning, but
now we`re starting to see fair weather cumulus fill in.
Additional cloud cover is filling in across WI tied to a
midlevel shortwave impulse spinning over northern MN. This wave
will dive SE across Lake Michigan later tonight, although it
shouldn`t amount to anything locally except perhaps some added
cloud cover, particularly around the lake.

As the windward side of the upper trough drops into the region
overnight, surface high pressure will follow suit and center
itself over the area early tomorrow. This will allow for a cool
start to the day with morning lows progged in the 20s. But
plenty of sunshine and some afternoon return flow should warm
temperatures slightly from this afternoon. Highs tomorrow are
forecast in the upper 40s to around 50. Upper height rises into
Sunday behind the departing trough will promote unseasonably
mild conditions to end the weekend with lower 60s favored around
the area Sunday afternoon. No precip is currently forecast over
the weekend.

More early summer-like temps appear on tap for Monday and
Tuesday, and this period will also be the one to watch for our
next shot at strong to severe convection around the region. On
Sunday, a sharp low amplitude upper trough will swing onshore
the PNW coast and dig eastward along the US-Canadian border
through Tuesday. The low level response will be a deepening
cyclone tracking across the northern Plains and upper Midwest
with associated cold front slated to pass over our area during
the latter part of Tuesday.

A strong warm advective regime will spread into the region in
advance of the approaching wave and should allow for 70s to
return to the area for Monday, maybe even near 80 degrees closer
to central and NW IL. 850mb temps will get up to near 15C by
late Monday and provide mid level lapse rates as high as 9-10
K/km. Models suggest some isolated to scattered convection could
get going in the storm`s open warm sector as early as Monday
evening and continue into the night. At this point, storms
during this time appear that they would be plenty elevated with
the low levels being so warm and maintaining lots of CIN. In
fact, this could very well inhibit storm development altogether.
Effective shear appears pretty meager as well, so if storms do
develop, they may struggle to organize. However, those lapse
rates aloft could perhaps still offer some deeper convective
cores, so will have to keep an eye on the late Monday period for
some stronger storms.

Additional severe convection may be in the cards around the
region again on Tuesday as the storm`s sharp cold front works
across. Still some disagreement on timing, but FroPa is progged
for sometime in the Tuesday PM window. How warm we`ll get during
the day is contingent on the timing of the front, but guidance
favors another day in the 70s to near 80 in spots. Medium-range
camps are in agreement on a developing line of convection along
the front as it moves across the area. Lapse rates aloft won`t
be nearly as steep by this time, but still respectable, and the
rather tall, skinny CAPE profiles on forecast soundings aren`t
very intimidating at first glance. However, storms will have a
better chance at going surface- based with little CIN and
seemingly strong forced ascent along the front making it easy
for BL parcels to convect. Plus, shear will be a little more
appreciable and deep layer saturation should limit entrainment.
So while convective parameters aren`t very impressive taken one
at a time, when you put them together, it could add up to a
pretty good environment for a line of strongly forced convection
along the front. The timing of the front will play a role in
the likelihood of strong storms locally, so will keep an eye on
model trends through the weekend.

Model certainty drops off after Tuesday, but if one thing`s for
sure, it`s that we`ll be cooling down again in the wake of the
front. Ensemble guidance favors highs in the 40s for the middle
of next week before milder conditions look to return prior to
the weekend.

Doom

&&

.AVIATION /18Z TAFS THROUGH 00Z SUNDAY/...
Issued at 1218 PM CDT Fri Mar 27 2026

.AVIATION...

Key Messages:
- North-northeast winds turning northwest for the afternoon,
  with gustiness (20-25kt) returning mid to late afternoon and
  evening
- Variable winds closer to KMDW with lower confidence on
  specific winds mid afternoon through early evening.

Winds are the initial concern, with varying winds in the vicinity of
ORD/MDW (NNE to NNW). Strong high pressure will move in from the
west through tonight, and this will trend winds toward NNW. This
should also help erode the lower clouds across the eastern half of
the airspace.  Given the weakening pressure gradient over the area
this afternoon, there may be a period of variability at KMDW, which
has a decent chance to shift back to NNE behind a lake boundary.
At this time confidence is higher that KORD will hold a NNW
versus a NNE direction for the period. KGYY will hold more of a
north-northeast wind as well.

There is a weak system moving through Wisconsin that will graze the
area, but at worst would lead to some lower VFR and MVFR cigs for a
short time overnight, but VFR is most likely. Winds that normally
ease in the evening will remain gusty out of the NNW ahead of this
system. Once the high move in overnight, winds will ease and then
transition to southwesterly on Saturday. Gusts will hold under 20 kt
on Saturday.

KMD

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 7 PM CDT this evening for the IN
     nearshore waters.

&&

$$

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